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Starlight Silver MG TF 135
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Discussion Starter · #1 ·
I have a 2002 TF135 (Manual Transmission of course). I am about to fit a simple (cheap!) low-coolant warning system, which has a buzzer to provide a low-coolant warning, but no warning light.

I can see that there is an (obviously) unused Gearbox Failure warning light for cars with Steptronic Transmission., see diagram and picture of back of instruments below:
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In the picture above, the back of the instrument panel circuit board shows a track running to the warning light I want to use circled in green.

My questions are:
1. Could I connect a wire to the screw in the centre of the green circle above. This wire will become live when low-coolant is detected by the system I am about to fit.
2. Will doing the above cause any problems?

Thanks for any information from those with better knowledge of this panel. Is access to the back possible without removing the whole assembly?
 

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First, if you remove screws on that printed circuit board be very careful when you put them back as board is very sensitive and only light tight with fingers is all that it needs.

Second, theoreticaly you can put wire below that screw, but in the same time you need to know that other side DO have ground connection.

Third, I would take percaution in order to see that you have direct electrical connection from that screw to the position on the connector where wire shoukd be in order not to pass through any additional electric element on the board.

Fourth, I would be sure that on connector side you have that pin empty without any wire on it. Because if you have then putting additional signal on that wire might cause problems on that circuit.
 

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2002 MG TF 135 VE51FTF
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Roverlike just a thought but wouldn't there be a pin (unused or missing) in the instrument cluster connector that could be used to light the bulb. I tried looking on the wiring diagram but just went blind! is there a hard copy of these available? it seems to be 300 pages which prob means 拢1K in ink
 

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As I can see it from electric diagram that lamp is internaly connected with LCD as well:

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With this in mind I would not suggest to apply any signal onto that line. However you can imsert LED inside which is independently powered.
 

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Starlight Silver MG TF 135
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Discussion Starter · #5 ·
Thanks for the thoughtful & helpful replies:
The advice about treating the circuit board carefully and ensuring that any new connection does not interferr with existing circuit is what I expected/anticipated, hence my original question.
Roverlike, are you sure that the circuit diagram you show below IS for the MGFmk2/early TF circuit board?
A warning light for "SPORT/SNOW" is shown. Nowt like that on my dashboard, nor any mention in my owner's manual. Sounds more like a 4-wheel-drive feature?? If it helps, the part number of my instrument panel PCB should be: YAH100790.
As I can see it from electric diagram that lamp is internaly connected with LCD as well:

View attachment 139495

With this in mind I would not suggest to apply any signal onto that line. However you can imsert LED inside which is independently powered.
I have looked more closely at the original picture of the back of the instruments. The other side of the aperture where a gear fail light would be, runs to a track marked "IGN", presumably "Ignition" I have highlighted this in Blue below
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This makes me think that it is the earth side of the warning light which is connected via the screw marked "GEAR" to an output of the ECU, or other circuit, which detects a servo failure in the automatic gearbox.

Looks like your suggestion of a completely independent bulb, fully insulated so that it makes no contact with the instrument panel PCB, would be the only safe way to use that warning light position on the display.
 

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I checked once again the diagram and it is correct one for early MG TF models with 5AS Lucas alarm box and MFU.

When you pointed out this IGN, I looked again into diagram and actualy IGN means you have power from that side. GEAR side actualy provides Earth/Ground connection and by that you cannot put signal/power on the side where GEAR is written when earth connection is expected from that side. I would say that if you measure voltage on the side of IGN you will have 12Volts there.

Regarding SPORT/SNOW light I was/am also puzzled since I do not know of such light on the cluster, but maybe worth to look into another cluster for automatic gearbox cars? I did not check if there is anothe cluster for automatic gearbox cars.
 

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Starlight Silver MG TF 135
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Discussion Starter · #7 ·
O.K. & Thanks for checking. As you say, I will not be able to use any of the circuits on that PCB, so the only way I can use that Warning Light Aperture is to insert an independently powered and earthed bulb or LED.
The Low-Coolant Alarm I am using is a kit from a guy called Bruce Cotsell. It looks like a well-designed kit, and he provides no less than 6 pages of advice/instructions of how to fit, including 14 pictures!. The sensor is contactless, and there is no need to drill or even remove the filler cap from the expansion tank. the complete system worked when I tested it attached to a Tupperware container part-filled with water, so it should be O.K. when installed on the Expansion Tank. I will post again with an appropriate title after I have installed it all and tested it for real, including hard cornering, acceleration & braking. There is no delay circuit in the system, so the occasional (hopefully brief) false alarm is to be expected.
 

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Discussion Starter · #8 ·
Answering my own question:
Thanks for any information from those with better knowledge of this panel. Is access to the back possible without removing the whole assembly?
I am now fairly confident that I CAN access the appropriate hole in the instrument panel PCB.
The photo below was taken blind with a small digital camera held facing towards the back of the instruments, above pedals. I can easily reach a finger into this area and can feel that hole. I may end-up removing the driver's seat to allow me to rest on my back, with my head on the pedals, so that I can see what I am doing. The Low-coolant sensor can drive a low-current LED, so a suitably insulated (to avoid connecting Live or Earth to existing PCB tracks) should do the job!
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I will post again when the job is done and fully tested.
 

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I checked SPORT light mentioned in the wiring diagram of instrument cluster. SPORT is displayed as part of digital odometer only in case of Steptronic 1.8 MGs. It is mentioned specialy on the diagram just to emphasize there is something special for Steptronic.
 

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2002 MG TF 135 VE51FTF
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EllisJo can I suggest if you have to go the hassle of removing the seat, why not remove the instrument panel instead? nice comfy seat to sit on whilst sorting where the wiring can go. Also you have probably thought of this already but it might be worth leaving some slack in the wiring in case you (having forgotten) or someone else attempts to remove the instrument panel in future.
Lastly in the picture it looks almost brand new, do you secretly hoover behind there, I'm sure mine didn't look that good when I removed it!!
 

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Starlight Silver MG TF 135
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Discussion Starter · #11 ·
Lastly in the picture it looks almost brand new, do you secretly hoover behind there, I'm sure mine didn't look that good when I removed it!!
Yep! It IS (surprisingly) clean back there, but most of this car is pretty clean: Only 23K miles and one (very) carefully P.O. so that probably accounts for general cleanliness.
I have discovered that I can lie half in/half out of car and get my head under the instrument panel to see what I am doing. Uncomfortable, but I think it works. No need for slack wiring: the complete light assembly will pull-away from the instrument panel PCB if any tension comes on the wires, as the light will be just a snug fit into the spare aperture, NOT bayoneted in.
 

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Discussion Starter · #12 ·
UPDATE:
I have now fitted the kit from MGF / MG TF - LOW COOLANT ALARM KIT - No Drilling Required - THE ORIGINAL! | eBay

Easy to install with excellent instructions I decided to also install a warning light LED, which involved threaded a twin-core length of cable underneath the carpet outboard of the seat. One wire to provide power for the Low-Coolant Alarm, the other to bring back a signal from the Alarm to power an LED inserted into the un-used warning-light hole which is used for transmission-failure warning on Steptronic Tx cars.

All working well now:
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The LED is in a piece of old plastic tube:
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I now have 4 spare LEDs pm me if you want to do the same mod or need a warning light for whatever.
 

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Job well done, might do a similar thing myself later this year my only concern is that no delay is fitted, can you report back as to how it performs in the real world re false alarms. Thanks
 

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Discussion Starter · #14 ·
Job well done, might do a similar thing myself later this year my only concern is that no delay is fitted, can you report back as to how it performs in the real world re false alarms. Thanks
Yes, will do. Weather totally unsuitable at present, but once I have tried it out with harsh braking & a bit of hard cornering on an empty road, I will let everyone know. One thing I LIKE, is that I get a brief "Peep" and the warning light flashes on at the same time, as I turn the ignition key to posn2. I like to know that the system is alive. Deepfat, I think you have my email from previous PMs, but if you want one of my spare LEDs, let me know.
I doubt if there will be many false alarms, I unbolted the tank to make cleaning the surface to be glued easier. This also allowed me to tilt the tank enough to trigger the alarm after attaching sensor. I had to tilt the coolant COMPLETELY clear of the surface facing the sensor to get a peep.
 

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I have a low coolant LED in the Cog Wheel light hole. It makes for a neat install. My ultrasonic sensor does a self check at ignition on which is useful. I considered using the grey/green wire from the ECU to the Speedo but decided agaiinst it. I would of needed to completely isolate the wire by cuting the wire just prior to the ECU and at the speedo end.before the multi plug and link to GEAR and then cut the track on the speedo circuit board.. The grey green wire carries a digital signal from the ECU to the speedo to show the driver what gear they are in. In the end I just ran 2 wires to the LED. The problem is that the speedo wants a switched earth but the sensor switches the +12 so I would have had to inculde a relay or some electronics to effect that.
 
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